The shocking effects are even worse among those who are already obese.

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SLIM SODA: Diet drinks may be just as bad as full-fat

What fizzy drinks do to your body

Click through our gallery to see what fizzy drinks are really doing to your body.

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They can cause early puberty - A Harvard Medical School study of 5,583 girls aged nine to 14 found that those who drank just one-and-a-half cans of soft drink a day had their first periods earlier than those who did not.

According to new research, downing four cans of sugar-free pop per day triggered proteins that fuel both fat and inflammation.

“Low-calorie sweeteners promote additional fat formation”

Professor Sabyasachi Sen

The study adds to growing evidence that switching to zero calorie diet drinks may make things even worse.

Professor Sabyasachi Sen, of George Washington University, US, said: "Many health conscious individuals like to consume low-calorie sweeteners as an alternative to sugar.

Researchers tested sucralose, which has the trade name Splenda, and is 600 times sweeter than sugar.

Sucralose is used in more than 4,000 products from fizzy drinks to low-fat flavoured milk, light yoghurt, cereal bars, cakes and sweets.

The scientists grew stem cells from human fat tissue in lab dishes for 12 days and exposed them to low-calorie sweeteners – the equivalent of four cans of diet fizzy drinks a day.

Sucralose increased expression of genes that are markers of fat production and inflammation. There also was increased accumulation of fat droplets in cells.

This is how much sugar is in your favourite drinks

Liverpool City Council have named and shamed the worst soft drinks companies. Highlighting just how much sugar is in our favourite fizzy drinks, they named and shamed the sweetest soft drinks and Lucozade was the worst offender.

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500ml of Coca-Cola has over 13 teaspoons of sugar

Professor Sen added: “From our study, we believe low-calorie sweeteners promote additional fat formation by allowing more glucose to enter the cells, and promotes inflammation, which may be more detrimental in obese individuals."

Last year another team of US researchers found another artificial sweetener, aspartame, can interfere with metabolism.

Aspartame is used in more than 6,000 products, including Diet Coke and Diet Pepsi, which also contains acesulfame potassium.

Researchers said the sugar substitute's breakdown product, phenylalanine, disrupts the metabolic rate and consequently ups the chances of weight gain.

Another previous study found drinking just two glasses of diet drinks a day more than doubled the risk of developing diabetes while having five or more sugar-free drinks a day increased the risk by 4.5 times.

Around 3.3million Brits have been diagnosed with diabetes and the majority have type-2, which is partly caused by obesity.